I would like to set up another fine offset WS with a RPi zero W. I installed mono 4.0.5 but the RPi answers "Illegal instruction" to "mono -V" whereas my RPi3b answers "Mono JIT compiler version 4.0.5..."
Same answer with mono version 3.10.
Search on the web gives an explanation: "It usually says "Illegal instruction" if you try to run a Pi3 binary on a Pi Zero."
If my RPi zero is in this case, do you know where I can download precompiled of mono 3.10 (or 4.0.5) for PiZero not for Pi3? or where to download sources and how to compile them?

Thank you mcrossley for your answer
But I did it 3 times: download a new img (stretch lite) install it on a microsd card, create ssh and wpa_supplicant.conf on the boot partition. Then by SSH, update and upgrade, install mono 3.10 (or 4.0.5.1-0xamarin0). Each time, the same result: "Illegal instruction" at mono -V or mono --version

I found the solution:
Among the multiple steps to setup the RPi zero W to work with mono and CumulusMX, at each time I changed the localisation options in raspi-config.
It seems it generated an "Illegal instruction" error for mono 3.1 or 4.0.5. This forth time I changed only the password of pi in raspi-config. Now mono is working well